The present invention generally relates to optical switches and more particularly to an optical switch and a switching method therefor for the switching of an optical signal through the use of a selectively positionable re-directing fiber.
In applications involving the transmission of optically encoded data through fiber optic cables, there is frequently a need to selectively switch data between an input fiber and two or more output fibers. A simple way to provide optical fiber switching has been to perform the switching manually. This may be accomplished, for example, by manually manipulating a switchboard panel. This solution, however, is limited to applications where the number of output fibers to be switched between is relatively small and a relatively slow switching time is acceptable.
Switching applications that require more rapid response and/or a relatively large number of output fibers typically employ an automated switching device. One kind of automated switching device is an opto-mechanical switching device. Opto-mechanical switching devices typically employ a lensed input fiber which is mechanically moved across a bank of lensed output fibers. Data is transferred when the lensed input fiber is aligned with a lensed output fiber.
Opto-mechanical switching devices typically have a switching response on the order of 10 to 50 ms, which is far better than that which is possible for a manually operated switchboard panel. Furthermore, opto-mechanical switches generally exhibit good cross talk, back reflection and insertion loss characteristics.
One drawback associated with conventional opto-mechanical switches concerns the ease and cost with which they are integrated into a circuit. Generally, the microlenses of a conventional opto-mechanical switch must be aligned to each fiber and testing must be performed to verify that the alignment is proper. In applications requiring relatively large switches, the cost of fiber alignment is a dominant cost and may easily exceed the cost of the switch itself.
One attempt to reduce the costs associated with opto-mechanical switching devices is disclosed in U.S. Pat. No. 5,621,829 entitled xe2x80x9cFiber Optic Switching Device and Method Using Free Space Scanningxe2x80x9d, the disclosure of which is hereby incorporated by reference as if fully set forth herein. The device of the ""829 patent employs a moving reflective mechanism, such as a reflector or a prism, to transfer a collimated light signal from the input fiber to a desired output fiber. This approach, however, has, several drawbacks. One drawback associated with the approach disclosed in the ""829 patent concerns the efficiency with which light is transmitted from the input fiber to an output fiber. The use of reflective mechanisms typically results in a total internal reflection or loss in efficiency of about 5 to 15 percent for the best reflective surfaces. Losses may be substantially higher for lower quality reflective surfaces, rendering it even more likely that the input signal will not be accurately transmitted to the preselected output fiber.
Another drawback concerns the relative cost of the device disclosed in the ""829 patent. Reflective mechanisms, especially those having good quality reflective surfaces, are typically expensive and as such, tend to increase the initial cost of the switching mechanism. Furthermore, periodic maintenance or cleaning of the reflective surface is required to maintain optical performance of the reflective mechanism and ensure maximum light transmission from the input fiber to the preselected output fiber.
It is one object of the present invention to provide an opto-mechanical switching device which does not require extensive alignment between an input fiber and a plurality of output fibers.
It is another object of the present invention to provide an opto-mechanical switching device which does not require expensive reflective mechanisms for transmitting an optical input to a predetermined output fiber.
It is a more specific object of the present invention to provide an opto-mechanical switching device which employs a re-directing fiber to accurately and efficiently transmit an optical input to a predetermined output fiber.
It is yet another object of the present invention to provide a method for switching an optical signal between a plurality of output fibers using a re-directing fiber.
In one preferred form, the present invention provides an opto-mechanical switching device for selectively switching an optical input between a plurality of output fibers. The opto-mechanical switching device includes a re-directing fiber adapted to receive the optical input. The re-directing fiber is selectively positionable to transmit the optical input to a predetermined one of the plurality of output fibers. A method for switching an optical input between a plurality of output fibers is also provided.